Power steering mechanism



Sept. 7, 1954 Filed April 17, 1952 2 Sheets-Sheet l ATTORNEVS Sept 7i1954 A. HAYNEs Erm. 2,688,258

POWER STEERING MECHANISM Filed April 17, 1952 2 Sheets-Sheet 2 iINVENToR ATTORNEVS Patented Sept. 7, 1954 POWER STEERING MECHANISM AlexL. Haynes, Detroit, and Warren A. Van Wickln, Jr., Dearborn, Mich.,assignors to Ford Motor Company, Dearborn, Mich., a corporation ofDelaware Application April 17, 1952, Serial No. 282,784

(Cl. 'I4-388) 7 Claims. 1

This invention relates generally to power steering mechanism, and hasparticular reference to a steering mechanism in which the manualsteering effort is augmented by a hydraulic power unit whenever thesteering load exceeds a predetermined amount.

An object of the present invention is to provide a power steeringmechanism in which hydraulic control mechanism for a hydraulic servounit is incorporated in the steering mechanism housing and is directlyactuated by means of a control member which in turn is actuated by thetorsional deflection of the steering post under load. In the presentinstance this is accomplished by means of a hydraulic `power cylinder orservo unit operatively connected to the steering shaft which carries thesteering pitman arm. The hydraulic servo unit is connected to a powersource and controlled by means of a hydraulic spool valve mounted in thesteering gear housing and concentrically surrounding the steering postintermediate the ends of the latter. One end of the post is connected tothe steering wheel while the opposite end carries a worm meshing withthe worm wheel carried by the steering shaft. Intermediate its ends, thesteering post is reduced in diameter so as to provide for torsionaldeection under load. An operating sleeve surrounds the steering post,being secured to the post at its upper end adjacent the steering wheel,and being arranged for free rotation relative to the post adjacent itslower end. The steering post and sleeve are formed with intersectingrelatively inclined slots through which a pin extends,

with the protruding ends of the pin secured to the valve spool so thatrelative angular movement between the steering post and the sleeveresults in axial movement of the pin and the valve spool. This axialmovement controls the flow of fluid to the opposite ends of the servounit to furnish power to the steering shaft and pitman arm whenrequired.

Still another object is to provide cooperating abutment means betweenthe steering post and sleeve, with a predetermined circumferentialclearance left therebetween, so that in the event of failure of thehydraulic mechanism steering effort may be transmitted through thesleeve to the worm gear to provide for manual operation and to limit therelative angular deflection between the post and sleeve.

A still further object of the invention is to provide power steeringmechanism which is compact and relatively inexpensive to manufacture andassemble, and which does not require extensive changes in theconventional type of steering mechanism. The mechanism embodies thedesired advantages of feel, reversibility and absence of appreciablebacklash. The mechanism permits steering under normal circumstances tobe accomplished without power assistance with no change in the backlashor response from that of the usual manual system, while at the same timeautomatically providing power assistance when steering loads require.Road reaction is transmitted to the steering wheel in the normal mannerbut is limited to a maximum value.

Other objects and advantages of this invention will be made moreapparent as this description proceeds, particularly when considered inconnection with the accompanying drawings, in which:

Figure 1 is a side elevational view of the power steering mechanism ofthe present invention.

Figure 2 is a vertical cross-sectional view taken on the plane indicatedby the line 2-2 of Figure 1.

Figure 3 is a longitudinal cross-sectional view taken on the planeindicated by the line 3--3 of Figure l, and in addition showing aportion of the steering wheel, with the hydraulic circuit shown indiagrammatic form.

Figure 4 is a cross-sectional view taken on the plane indicated by theline 4 4 of Figure 1.

Figure 5 is a vertical cross-sectional view taken on the plane indicatedby the line 5-5 of Figure 2.

Figure 6 is a cross-sectional view, partly in elevation, taken on theplane indicated by the line 6-6 of Figure 3.`

Figure '7 is a cross-sectional view taken on the plane indicated by theline 'I-l of Figure 6.

Figure 8 is a fragmentary cross-sectional view taken on the planeindicated by the line 8 8 of Figure 3.

Referring now more particularly to the drawings, the reference characterI I indicates the housing of the steering mechanism of the presentinvention. Supported within the housing II is a generally verticalsteering shaft I2, rotatably mounted therein by means of bearings I3. Aconventional pitman arm I4 is splined to the lower end of the steeringshaft I2 and is connected by conventional linkage (not shown) to thesteerable front wheels of a motor vehicle. At its upper end the steeringshaft I2 rotatably supports a worm wheel I6 which in turn meshes with aWorm I1 mounted upon the lower end of a steering post I8 extendinggenerally at right angles to the steering shaft I2. The worm wheel I1 isrotatably mounted in the housing II by means of anti-friction bearingsI9. At its upper end the steering post I8 is keyed to a steering wheel2I.

The mechanism thus far described is conventional and is commonly used inmanual steering gear mechanisms. For the purpose of providing powerassistance to the steering mechanism, the housing II is formed with anintegral cylinder 22 extending generally at right angles to the steeringshaft I2 adjacent the lower end of the latter. Reciprocally mountedwithin the cylinder 22 is a piston 23 having spaced piston heads 24interconnected by means of axially extending struts 2E. Pins 21 extendinwardly from the piston heads 24 and engage opposite sides of a roller28 rotatably mounted upon the end of a crank arm 29 by means of bearings3l. The crank arm 29 is splined tothe steering shaft I2 intermediate theconnections of the latter to the pitman arm I4 and the worm wheel I6.

For simplicity of manufacture and assembly, the integral cylinder 22 isformed with open ends which are closed by cylinder heads 32 held inplace by retaining rings 33. Leakage is prevented by means of O rings 34mounted in peripheral grooves in the cylinder heads 32. As best seen inFigure 5, the cylinder heads 82 are formed with axial passages 36communicating with conduits 31 connected to the enlarged extensions 38of the cylinder heads. It will beapparent that when fluid pressure issupplied to one end of the cylinder 22 the piston 23 will be movedaxially, rotating the crank arm 29 and consequently the steering shaft'I2 to provide power assistance to the latter.

The invention incorporates compact and simplied means for controllingthe supply of fluid pressure to the double acting cylinder 22 inaccordance with the requirements of the steering load, so as to bringthe power unit into operation to assist manual steering when the loadexceeds a predetermined amount. Referring now particularly to Figure 3,it will be noted that the'steering post I8 has an intermediate portion4I which is reduced in diameter so as to increase its ability totorsionally deflect under load. This .torsional deection is utilized toactuate a hydraulic valve which in turn controls the double actinghydraulic cylinder and piston assembly.

Concentrically surrounding the steering post I8 between the connectionsof the latter to the worm I'I and steering wheel 2| is a control-sleeve42. The sleeve 42 is connected to the upper end of the steering post I8by means of a pin 43 so.

as to insure simultaneous rotative movement of the upper portions of thepost and sleeve. Adjacent its lower end the control sleeve 42 is formedwith inclined slots 44 and 46 on'opposite sides thereof. An examinationof Figures 6 and 8 will show that the slots 44 and 4S on opposite sidesof the control sleeve are oppositely inclined with respect to eachother, and are Veach inclined with respect to a plane normal `to theaxis of the sleeve. The steering post 4I is also provided with anelongated slot 41 extending axially and intersecting the slots 44 and46.

A pin 48 extends through the slots 44, 46 and 41 in the sleeve and post,and extends beyond opposite sides of the sleeve. It will be apparentthat the construction is such that any relative rotation between thelower ends of steering post I8 and the control sleeve 42 will result in:an axial movement of the pin 48 by reason of the relatively inclinedslots 44, -46 and 41. The control sleeve 42 is relatively rigid whereasthe steering post I8 with its reduced section 4I is adapted to betorsionally distorted under load. The steering post I8 is constructed sothat under normal steering conditions, such as in straight aheaddriving, the post torsionally distorts very little. When, however, agreater steering load is imposed, as for example during turning orparking or when road obstacles are encountered by the tires, the reducedportion of the steering post torsionally distorts a material amount. Itstorsional deflection relative to the rigid control sleeve 42 results inaxial movement of the pin 48.

With reference to Figure 3, the steering mechanism housing II isprovided with an enlarged bore 49 of a diameter suflicient to permit theworm gear I1 I-to be inserted therethrough into position in mesh withthe worm wheel I6. An outer bearing ring 5I is then inserted in the bore49 and is held in place by a retaining ring 52. Next, a valve sleeve 53is vinserted into the bore 49 in the housing, and is properly `locatedaxially and held in its assembled position by means of a threaded'endportion 54 engaging a correspondingly threaded portion `of vthe housing.A lock ring 55 locks the valve sleeve 53 against inadvertent axialdisplacement.

The valve sleeve 53 is provided with O ring seals 51 adjacent each endthereof to prevent leakage. The valve sleeve 'is also provided with aseries of ports 59, 60, 6I, 62 and lt3 -formed therethrough.

The ports 59 and 6I communicate with conduits 64 and GSrespectively(shown diagrammatically) which in turn join with each other in a commonreturn conduit 61. The conduit 61 feeds into a reservoir tank and lterunit 68, the latter communicating by means of a conduit 69 with a pump1I. The pump '1I may be of any convenient type and may be driven asdesired either from engine components or from a separate electric powersource. The output of the pump 1I is supplied through a supply conduit12 to the central port 60 of the valve sleeve y53.

The ports 62 and 63 of the valve sleeve 53 communicate by means vofconduits 31 with opposite ends of the cylinder 22 in the manner showndiagrammatically in Figure 3.

Slidably mounted within the valve sleeve 53 is a reciprocable valvespool 18, also provided with O ring seals 11 at opposite `ends thereof.The valve spool 18 is formed with a pair of circumferentially extendingannular grooves 18 and 19 in its -outer periphery. In the neutralposition of the valve spool as shown in Figure 3, the land between theannular grooves 18 and 19 is aligned with supply port AGII from the pump1I, but being slightly smaller than the port 60 permits uid at lowpressure to circulate through the system, being returned to the ytankandfilter unit through the ports -59 and 6I, and the passages 64, 66 and61. A relief valve 82 in bypass conduit .8I limits the pressure to apredetermined maximum when the power unit is operating.

The end ofthe valve spool 16 is provided with an annular recess 83receiving the protruding ends of the pin 48, the latter being held inposition by means of a washer .84 and a retaining ring 86. It will beapparent from the foregoing that the valve spool 16y will be movedaxially with the pin 48 in response to relative angular movement betweenthe steering post I8 and the control sleeve 42.

When the load upon the steering mechanism is sufficient to torsionallydeflect .the vreduced portion 4I of the steering post I8 the resultingrelative angular movement between the steering post and the controlsleevewill result in an axial movement of the pin 48 in one direction orthe other dependent upon whether the steering load is in a right or leftturn direction. When this axial movement of the pin 48 and the valvespool 16 connected thereto is sufficient to shift the latter axiallyenough to close communications between supply port 60 and either annulargroove 18 or 19, it willbe seen that communication isy established frompump 1I to supply conduit 12 and support port 60 to the particularannular groove' 18 or 19 in the valve spool and thence to either theport 62 or 63 as the case may be. Fluid pressure is thus supplied to oneend of the hydraulic power cylinder 22 and the double headed piston 23is axially moved therein. This results in angular movement of the crankarm 29 carried by the steering post I2 and the resulting powerapplication augments the manual steering effort. At the same time, theopposite end of the hydraulic power cylinder 22 communicates through theconduit at the opposite end of the 'cylinder and the corresponding port62 or B3 in the valve sleeve and thence through either the annulargroove 18 or 19 in the valve spool to the return port 59 or 6I. Thereturn fluid then returns through conduit 61 through the tank and filterunit 88 and conduit 69 to the pump 1I. During power assisted steeringthe manual effort is still applied through the steering post I8 to -theworm wheel so that the driver retains sufficient feel to enable him toproperly control the Vehicle.

Means are provided to enable heavy steering loads to be applied throughthe mechanism manually in the event of failure of any portion of thehydraulic system. As best seen in Figures 3 and '7, the inner end of thecontrol sleeve 42 is provided with a pair of diametrically opposedgrooves 81. The grooves 81 receive diametrically opposed lugs 88extending outwardly from and integrally formed upon the steering post I8adjacent the inner end of the control sleeve 42. It will be noted thatthe grooves 81 have a greater circumferential dimension than thecorresponding circumferential dimension of the lugs 88 so that clearanceis provided between opposite ends of the grooves and the adjacent lugs.VThis clearance is suincient to permit free relative rotation betweenthe inner end of the control sleeve 42 and the adjacent portion of thesteering post to permit the relative torsional movement necessary tocontrol the hydraulic power mechanism. Upon the failure of the hydraulicmechanism, however, the lugs 88 will eventually abut one end of thegrooves 81 to enable torque to be transmitted through the relativelyrigid control tube 42 to the inner end ofthe steering post I8 so thatheavy steering loads can be manually controlled.

It will be apparent that the degree of power assistance supplied throughthe hydraulic cylinder 22 is dependent upon steering requirements. Apredetermined torsional deflection of the reduced portion 4I of thesteering post I8 will result in suilicient axial movement of the valvespool to provide a restricted passage for the supply of Iiuid pressureto one end of the power cylinder. If the steering load increases and thetorsional deiiection of the steering post is correspondingly greater,the valve spool will move axially a further amount and increase theopening `from the pump to the power cylinder.

It will be understood that the invention is not to be limited to theexact construction shown and described, but that various changes andmodications may be made withoutV departing from the spirit and scope ofthe invention, as dei-ined in the appended claims.

What is claimed is:

l. In a steering gear mechanism, a steering gear housing, a steeringgear member rotatably mounted in said housing, a steering post havingone end rotatably mounted in said housing and operatively connected tosaid member to provide for manual operation of said member, a steeringwheel secured to the opposite end of said steering post, a hydraulicservo unit supported upon said housing and operatively connected to saidmember to provide for power operation of said member, a hydraulic powersource, a hydraulic valve spool reciprocably mounted within said housingconcentric with and surrounding said steering post, meansinterconnecting said power source, valve spool and servo unit to enablesaid servo unit to be controlled by said valve spool, a sleeve betweensaid valve spool and said steering post, said sleeve having a portioncontained within said housing and a portion projecting outwardly fromsaid housing, means connecting the outer end of the outwardly projectingportion of said sleeve to said steering post for rotation therewith as aunit, the inner end of said sleeve being mounted for rotative movementrelative to said steering post, and means associated with said steeringpost and said sleeve arranged to be moved axially upon relative rotationbetween said steering post and the inner end of said sleeve. resultingfrom torsional movement of said steering post under steering loads, saidlast named means being connected to said valve spool to axially move thelatter to actuate said servo unit and apply power to rotate saidsteering gear member.

2. The structure defined by claim 1 which is yfurther characterized inthat said last named means comprises a pin extending through saidsteering post and the inner end of said sleeve and projecting beyond theopposite sides of said sleeve, means connecting the projecting ends ofsaid pin to said valve spool, said steering post andsaid sleeve beingprovided with intersecting slots angularly related to each other throughwhich said pin projects, said angularly related slots axially movingsaid pin upon relative rotation between said steering post and the innerend of said sleeve.

3. The structure deiined by claim l which is further characterized inthat said last named means comprises a pin extending through saidsteering post and the inner end of said sleeve and projecting radiallyoutwardly from said sleeve, means connecting the outer ends of said pinto said valve spool, said steering post having an axially extending slotformed therein through which said pin projects, and said sleeve having apair of slots formed on opposite sides thereof through which said pinprojects, the two slots in said sleeve being inclined with respect tothe axis of said sleeve with said slots in the sleeve being inclined inopposite directions.

4. The structure dened by claim l which is further characterized in thatthe inner end of said sleeve and the adjacent portion of said steeringpost are provided with angularly spaced abutments, said abutments beingspaced circumferentially from each other a predetermined amount so thata limited relative rotation between said sleeve and said steering postis permitted in each direction afterwhich relative movement kkthe saidabutments engage each other preventing further rotation between saidsleeve and said steering post and permitting manual operation of saidsteering mechanism in the event of failure of any portion of thehydraulic power system.

5. In a steering gear mechanism, a steering gear housing, a steeringgear member rotatably mounted in said housing, a steering post havingone end rotatably mounted in said housing and operatively connected tosaid member to provide for manual operation of said member, saidsteering post projecting outwardly from said housing and having anintermediate portion reduced in cross-section to allow torsionaltwisting of said steering post under steering loads, a steering wheelsecured to the outer end of said steering post, a hydraulic servo unitsupported upon said housing and operatively connected to said steeringgear member to provide for power operation of said member, a hydraulicpower source, a ported valve sleeve xedly mounted within said housingconcentrically surrounding said steering post and radially spacedtherefrom, an axially movable hydraulic valve spool slidably mountedwithin said valve sleeve, means interconnecting said power source, servounit and valve sleeve t enable said servo unit to be controlled by theaxial position of said valve spool in said valve sleeve, an elongatedsleeve between said valve spool and said steering post, said lastmentioned sleeve having an inner end within said housing and an outerend projecting outwardly from said housing and surrounding the reducedportion of said steering post, means connecting the outer end of saidsleeve to said steering post near the outer end thereof, the inner endof said sleeve being mounted for relative rotation with respect to theadjacent portion of said steering post, the inner end of said sleeve andthe adjacent portion of said steering post having elongated slotsextending radially therethrough with said slots intercepting each otherand being inclined to each other, a pin extending through the slots insaid sleeve and said steering post and having projecting ends secured tosaid valve spool to move the latter axially upon relative rotationbetween said steering post and the inner end of said sleeve resultingfrom torsional twisting of the reduced portion of said steering postrelative to said sleeve under steering loads.

6. In a steering gear mechanism, a steering gear housing, a steeringgear shaft rotatably mounted in said housing, a steering postrotatablymounted in said housing at right angles yto said 1 first,mentioned shaft, a gear mounted upon the innerend of said steeringpost, a-second gearfmounted upon said Vsteering shaft and meshing ywithsaid Vfirst mentioned gear, a steering wheel secured to the oppositeouter end of said steering post, `said steering post having a portionbetween said rst mentioned gear and said steering wheel reduced indiameter to enable said steering post to be torsionally twisted understeering loads, asleeve surrounding the said intermediate portion ofsaid steering post, means rigidly connecting .the outer end of saidsleeve to said steering post adjacent the outer end of the latter,.a pinprojecting dia.- metrically through said steering post and said sleeveintermediate the reduced portion of said steering post and the -rstmentioned gear on said steering post, said steering post and said sleevebeing formed with intercepting slots angularly inclined with respect toeach other ythrough which said pin projects, a hydraulic servo unitmounted upon-said housing and engageable with said steer, `ing shaft toprovide for power operation of the latter, a hydraulic pump, hydraulicvalve means slidably mounted in said housing concentric with saidsteering post and said sleeve and surrounding the latter, meansestablishing communication between said hydraulic pump, servo unit andvalve means to actuate said servo unit and said steeringshaft upon axialmovement of said valve means, and means securing a projecting portion ofsaid pin to said valve means to axially move the latter upon relativetorsional movement between said steering post and said sleeve.

7. The structure dened by claim 6 which is further characterized in thatthe inner end of said sleeve is formed with a circumferentiallyextending slot, a radially outwardly extending projection upon saidsteering post received within the slot in said sleeve, thecircumferential dimension of said projection on the steering post beingsmaller than the corresponding dimension of the slot in said sleeve soas to provide clearance therebetween and permit a predetermined relativerotative movement between said steering post ,and said sleeve, saidprojection abutting one end of the slot in said Vsleeve upon apredetermined relative rotation between said sleeve and said steeringpost to provide for manual operation of said'steering gear mechanism inthe event of failure of any portion of the hydraulic system.

No references cited.

